This invention relates to a remote controlled actuator and electronic control. The actuator may be used to adjust the phasing or external receiving or transmitting element of an antenna such as used in cellular and other systems. Additionally, this invention relates to a digital power converter that may be used separately in various applications as well as providing power for driving the motors of controlled actuators. The actuator system will also have a wide variety of other uses where the application demands characteristics, such as: Low EMI (low electromagnetic emissions), stable current and voltage control to the motor coils over long cables, a minimum of conductors in the cable, non-volatile, absolute position feedback and low cost. Additionally it is advantageous to not have fragile electronic components in the remote actuator due to the potential hazards of nearby static electricity and lightning hazards.
Remote actuators for antenna systems have been previously suggested. In the system described U.S. Pat. No. 6,239,744; there are remote antenna actuators each having a separate remote micro controller with a main controller at a different location. Each of these remote controllers would be susceptible to the elements including static electricity and lightening. Use of sensors to determine remote actuator position has been known as described in the ""744 patent, it however did not do remote actuator position sensing from a resistance change due to motor linear drive shaft movement.
In the prior art there have been dual polarity bipolar power drive circuits. These circuits could only have bi-level voltage supplies by having separate power supplies at the different voltages.
What is needed and does not exist in the prior art are sets of multiple remote controlled actuators that do not need more than one electronic controller and do not need to have an also remotely located electronic controller. Also a remote actuator is needed that has low EMI characteristics, stable current and voltage control to motor coils over long cables, a minimum of conductors in the cable, non-volatile, absolute position feedback. Also needed is a remote actuator sensor that provides accurate actuator position from linear drive shaft movement. Also needed is a dual polarity multi-level power converter that does not require different voltage sources.
An object of the invention is to provide a remote controlled actuator that does not need more than one electronic controller and does not need to have an also remotely located electronic controller. Also an object of this invention to have a remote actuator that has low EMI characteristics, stable current and voltage control to motor coils over long cables, a minimum of conductors in the cable, and non-volatile, absolute position feedback. An additional object is to provide a remote actuator position indicator that determines position from a motor linear drive shaft. Another object of the invention is to provide a dual polarity multi-level power converter that does not require different voltage sources.
The remote controlled actuator of this invention satisfies all the objects of the invention and others not mentioned. In its broadest embodiment, the actuator system has a motor with a drive or screw shaft. The motor may drive a nut or piston that rides on the screw shaft. The motor may be a two-phase brush-less motor known as a step or stepper motor. The control circuit may include two or more steering diodes to minimize wires for position sensing where there are two or more actuators being driven remotely. A remote controller may direct motor movement of individual actuators without a local to the motor controller. There is a multi-level drive circuit to provide the step voltage to boost current flow and then to reduce the voltage once the motor current reaches the desired level. The control circuit commutates the motor coils by alternating the drive polarity by using pulse width modulation techniques vary the voltage anywhere between the positive and negative voltage rails. In one embodiment the multi-level drive circuit is a dual polarity multi-level power converter that does not require more than one power source. More importantly the multi-level power converter acts to stabilize the voltage of two different power rails while a pulse width modulator is used to vary the duty cycle input signal and hence provide varying levels of power of dual polarity. The multi-level power converter may be used in other applications beyond driving motors no less for driving motors for positioning cellular antennas.
The mechanical actuator may have a barrel or other mechanical guideway that may be made of plastic or metal containing a sliding piston or member which is threaded as a nut that is propelled by a motor lead screw shaft and also accomplishes a linear bearing means. The barrel may have an internal keyway along with an anti-rotation sliding or rotating bearing protected against rotation by the keyway. This anti-rotation sliding bearing restricts the piston to linear travel along the driving motor lead screw thread. These features form a linear actuator when used with a motor such as a step motor.
The position sensor may include a resistive element sliding contact mounted to the sliding piston. The sliding contact bridges between two tracks on the resistive element to create an electrical potentiometer whose resistance will be a function of the position of the piston. Where used, the electrical contacts are connected to a circuit, which can read or relay this position information using electrical current or voltage to the main controller.
The piston may be mechanically engaged to drive an object, for example a phasing element of an antenna or for changing down angle of a cellular antenna on a cellular tower. The motor may be used to position the piston that in turn positions the phasing or receiving element of the antenna. Such repositioning of the phasing or receiving element of the antenna may change the response or performance of the system, cellular or otherwise, which is in electrical connection with the phasing or receiving element. There is an additional advantage relating to installation and service due to the coaxial like mechanical connector with two sets of threads between the actuator barrel and the outer body or bushing of the object to be actuated and the internal threading between the piston and the control rod of the object to actuated. When the object to be actuated is a cellular antenna and the actuator is changing down angle of the antenna, servicing personnel are required to access these antennas high up on towers. The coaxial like engagement allows for proper installation with less effort. Additional effects, features and advantages will be apparent in the written description that follows.